The lower esophageal sphincter (LES) and pylorus play important roles in controlling the transit of substances from the stomach. Numerous hormones, peptides and neurotransmitters have been shown to have an effect on these sphincters. The specific agents and mechanisms which control sphincter reflexes in vivo remain ill defined. Myoelectric recordings have been used to define the mechanisms of motor function in many areas but only limited studies on the myoelectric correlates of LES and pyloric function are available. These studies will evaluate the mechanisms through which the LES and pylorus respond to intrinsic reflexes. First, we will quantitate the myoelectric correlates of sphincter function. Specifically these studies will clarify the significance of spike discharges in the recording of phasic and tonic sphincteric contractions. Second, to determine how the underlying myoelectric properties of these sphincters control the way in which the sphincter responds to stimuli. Third, to determine the location and specificity of receptors that initiate the reflex control of spincter tone. Fourth, to determine the specific transmitter agents and pathways involved in these reflexes. It is anticipated that the identification of factors which act to regulate sphincter function will lead to an increased understanding of the disease mechanisms that effect these sphincters.